1. Field of the Invention
The present invention relates to a self-propelled colonoscope, which does not cause pain to a patient during a colonoscopic examination for the colon.
2. Description of the Related Art
Colonoscopic examination is currently carried out by inserting a colonoscope by hand, so the examination may cause pain to a patient by excessively extending or bending the colon.
FIG. 6 is a drawing schematically showing an insertion path of a conventional colonoscope.
The tip of insertion tube 100 of the colonoscope is inserted from the anus 101 into the colon 103 and advances from the sigmoid colon 105 to the ileum 113, by passing through the descending colon 107, a transverse colon 109 and an ascending colon 111. The tip of the insertion tube 100 may be inserted until it reaches the distal end of the colon 103 (A) or it may be inserted into the ileum 113 for about 25 cm (B).
As shown in FIG. 6, the sigmoid colon 105, positioned near the insertion point of the colonoscope, is sharply bent in an S-shape. As a consequence, considerable operator skill is necessary to pass the insertion tube 100 through this portion. Further, the procedure causes increased pain to the patient.
And, the diameter of the insertion tube of a colonoscope conventionally used is 11.3 to 14.2 mm in general. When the tip of the colonoscope advances into the colon while bending, as shown in FIG. 6, the inner circle length and the outer circle length of the inserted bending insertion tube are different. So, in order to make the insertion tube advance steadily adjusting to the bend of the colon, a length of the inserting tube needs to have an allowance corresponding to the difference between the lengths of the inner circle and the outer circle of the inserted insertion tube while the insertion tube is bending.
In view of the above problems, it is an object of the present invention to provide a colonoscope which causes less pain to a patient and is able to be stably inserted.
According to an aspect of the present invention, a colonoscope is provided with a insertion tube comprising a distal section, a bending section and a flexible section, a lattice of a fiber of an image sensor element or an image-guide and a lattice of a fiber of a light-guide at the above-mentioned distal section, and an endless belt, which is sent out to the surface of the above-mentioned flexible section, from a guide hole near the tip of the flexible section, by driving a driving unit mounted at a driving unit casing, and reaches the same guide hole again through the above-mentioned driving unit, the endless belt being arranged on the surface of the above-mentioned flexible section, whereby the colonoscope is self-propelled into a colon by driving the endless belt. The length of said endless belt is 102 to 104% of a length such endless belt would be if it were tensely held at one end by the guide hole near the tip of said flexible section and at another end by the above-mentioned driving unit, while the flexible section was held straight.
On the surface of the flexible section, the endless belt, which passes out to the surface of said flexible section from the guide hole near the tip of said flexible section and returns to the driving unit, is driven by the driving unit, mounted at the driving unit casing, so that friction between the endless belt and an inner surface of the colon is able to make the colonoscope self-propelled. Since the colonoscope is self-propelled and adjusted to the shape of a colon, the colon is not extended or bent excessively, so that less pain is inflicted upon the patient.
On the other hand, the distal section of the insertion tube of the colonoscope inserted into the colon advances while adjusting to bent shapes of each part of the colon from the sigmoid colon to the ileum, through the descending colon, the transverse colon and the ascending colon. The diameter of the flexible section is 11.3 to 14.2 mm in general. Thus, when the tip of the insertion tube advances into the colon while bending, the inner circle length and the outer circle length of the inserted insertion tube are different. When the tip of the insertion tube reaches the ileum, the insertion tube will turn around, so that if the diameter of the insertion tube is 11.3 mm, the outer circle length of the tube is 2.2% longer than the straight length of the tube, and if the diameter is 14.2 mm, it is 2.77% longer. In the case of a self-propelled colonoscope in the present invention, the optimum diameter of the insertion tube is 16 mm so that the outer circle length is 3.12% longer.
Thus, it is necessary to set the length of the endless belt, arranged on the surface of the insertion tube, to have allowances corresponding to such differences. The length of the endless belt is 102 to 104% of the length of the endless belt, when the endless belt tensely turns around, from the guide hole near the tip of the flexible section of the insertion tube to the same guide hole, through the driving unit, while the insertion tube is maintained straight. So, the endless belt can sufficiently follow the bend of the insertion tube to be able to advance the colonoscope into the colon stably.